Method of producing wooden articles of circular cross section and varying diameter, and the resulting article



Dec. 10, 1946. 'c. B. LUNDSTROM METHOD OF PRODUCING WOODEN ARTICLES OF CIRCULAR CROSS SECTION AND VARYING DIAMETER AND THE RESULTING ARTICLE Filed Nov. 28, 1944 Fiel FiG.3

3nventor attorneys Patented Dec. 19, 194-6 UNITED STATES PATENT OFFICE METHOD OF PRODUCING VJOODEN ARTI- CLES OF CIRCULAR CROSS SECTION AND VARYING DIAMETER, AND THE RESULT- IN G ARTICLE 2 Claims.

1 This invention relates to a method of producing slender wooden articles and the resulting article. The conventional way of producing slender wooden articles which are circular in cross section and which have varying diameters throughout their length is to turn them in a lathe. Typical examples are the spindles used in chairs and other pieces of furniture. As a consequence, an article so turned is weakest in its small section. The invention produces a similar article which is nearly indistinguishable from a similar turned article and which nevertheless is quite strong in its slender sections, at any rate, very much stronger than a similar turned article would be.

The following invention is intended particularly for the manufacture of furniture components. It may be used in the manufacture of any wooden article which is circular in cross section and of varying diameter. It affords particularly desirable results under conditions requiring good mechanical strength.

It is well known that wood may be plasticized by impregnating it with urea or thio-urea or a mixture thereof and may then be densified by compressing it transversely to the grain in heated dies (see the patents to Loughborough 2,298,017, October 6, 1942, and 2,313,953 March 6, 1943). With certain woods, water if present in proper quantity will serve as a plasticizer.

The present invention produces slender components by plasticizing a suitably dimensioned slender blank and then variably densifying the blank by transverse compression to produce the desired varying cross section. In consequence the slenderest sections are the most densified and hence the strongest, a novel and valuable attribute. If the variations in dimension of the finished spindle exceed what can be attained by varying the densification, the blank may be formed to relieve the excess.

The invention will now be described as used in the formation of a spindle, reference being made to the accompanying drawing, in which Figure 1 is an end elevation of the roll structure.

Figure 2 is a section on the line 2-2 of Figure 1.

Figure 3 is a view of the finished spindle made in the rolls of Figures 1 and 2, the outline of the blank from which it was formed being indicated in dotted lines.

The spindle is formed by axial rolling and a typical roll stand is indicated in Figures 1 and 2. This stand has two end frames 5 and 6 in which are journaled two of three identical forming rolls 1. The third of the three rolls 1 is journaled at its ends in two frames I l and [2 which are guided vertically in the corresponding end frames 5 and i5. Thus the two lower ones of the rolls 1 turn on fixed axes and the third roll I is moved toward and from the other two. Each of these rolls has knurled end portions 8. Any or all of the three rolls may be driven, but it is more convenient to drive one or both of the lower two. The configuration of all the rolls is the same.

Assume that it is desired to produce a spindle such as that shown in Figure 3 which has a central enlargement A and end portions B of approximately the same diameter as said central enlargement and intermediate slenderer portions C. In such case the rolls would all be formed as is the top roll, clearly visible in Figure 2.

To produce the densified spindle a cylindrical blank whose outline is indicated in dotted lines at 13 in Figure 3 is plasticized and then placed between the rolls with the top roll in its elevated position. The plasticizing operation may, if desired, include the step of heating the blank. The rolls are suitably heated, and while they are being rotated, the top roll is slowly moved downward The efiect is to densify the wood of the blank in varying degrees according to the configuration oi the three forming rolls. The knurled portions 8 on the rolls will serve to drive the blank from the driven roll or rolls and will ensure rotation of any idle roll.

Since the invention is concerned with the general principle or method, and the resulting article, no attempt has been made to elaborate the details of the roll stand. Axial rolling is a known procedure in other arts and the roll stand itself is not claimed in the present application.

What is claimed is:

1. The method of producing a wooden article of the type described which comprises plasticizing a slender Wooden blank in which the grain of the wood runs longitudinally, and then axially rolling said blank between heated forming rolls which are of similarly varying longitudinal contour, and are caused to approach each other gradually during the rolling operation whereby the blank is densified in varying degrees at difierent points in its length and becomes set as a solid of revolution of varying cross section in which the degree of densification varies in inverse relation to the cross section.

2. A densified wood article of the type described, in which the article is a slender solid of revolution of varying cross section, the wood grain runs longitudinally, and the densification is evidenced by radial condensation of the grain, said densification varying in inverse relation to the cross section.

CARL' BRYNOLF LUNDSTROM. 

